Orthotic intervention in forefoot and rearfoot strike running patterns

Abstract

Objective. To compare the differential effect of custom orthoses on the lower extremity mechanics of a forefoot and rearfoot strike pattern.

Design. Fifteen subjects ran with both a forefoot and a rearfoot strike pattern with and without orthoses. Lower extremity kinematic and kinetic variables were compared between strike pattern and orthotic conditions.

Background. Foot orthoses have been shown to be effective in controlling excessive rearfoot motion in rearfoot strikers. The effect of orthotic intervention on rearfoot motion in forefoot strikers has not been previously reported.

Methods. Five trials were collected for each condition. Peak rearfoot eversion, eversion excursion, eversion velocity, peak inversion moment, and inversion work were compared between conditions. Kinematic variables in the sagittal plane of the rearfoot and in the frontal and sagittal plane of the knee were also determined.

Results. Increased rearfoot excursions and velocities and decreased peak eversion were noted in the forefoot strike pattern compared to the rearfoot strike pattern. Orthotic intervention, however,did not significantly change rearfoot motion in either strike pattern. Reductions in internal rotation and abduction of the knee were noted with orthotic intervention.

Conclusions. Foot orthoses do not differentially effect rearfoot motion of a rearfoot strike and a forefoot strike running pattern. Orthotic intervention has a larger and more systematic effect on rearfoot kinetics compared to rearfoot kinematics.
Relevance

Due to the similarity in response to orthotic intervention, foot strike pattern should not be a factor when prescribing a foot orthoses for controlling rearfoot motion.

Introduction

The effects of orthotic intervention on rearfoot motion have been studied extensively. While some studies have shown no effect (McCulloch et al., 1993; Stacoff et al., 2000; Nawoczenski et al., 1995) others have reported a reduction in some component of rearfoot motion including peak rearfoot eversion (Bates et al., 1979; Rodgers and Leveau, 1982) total rearfoot range of motion (eversion excursion) (Baitch et al., 1991; Novick and Kelley, 1990), and rearfoot eversion velocity (Smith et al., 1986). Some of the discrepancy in the literature is related to the small (but perhaps clinically relevant) effect size combined with high variability in response to orthotics and relatively low subject numbers in many of the studies.

All orthotic studies to date have been performed on runners who strike the ground with their heel first (rearfoot strikers). However, there are individuals who do not utilize this type of strike pattern when running. Kerr et al. (1983) filmed a total of 753 runners during a 10-km road race and a marathon and reported that nearly 20% made initial ground contact with their midfoot or forefoot. Additionally, a survey study reported that 27% of males and 39% of females strike the ground with their forefoot (the authors did not specify whether their group included sprinters who are mostly forefoot strike (FFS) runners) (Brunet et al., 1990).

FFS runners have been shown to exhibit different rearfoot mechanics compared to rearfoot strike (RFS) runners (McClay and Manal, 1995). RFS runners land in approximately 5° of rearfoot inversion and evert to approximately 10° of eversion at midstance. FFS runners exhibit similar peak eversion values at mid-stance compared to rearfoot strikers but contact the ground in a greater degree of inversion, resulting in greater eversion excursions and eversion velocities. Foot orthotic devices (FODs) are designed to provide rearfoot control in early stance, when the heel is on the ground. While the heel may contact the ground during mid-stance in a FFS pattern, the rearfoot is not in contact with the ground in early stance when orthotics are purported to provide rearfoot control. Therefore, a FFS pattern may be a contraindication for the prescription of a biomechanical foot orthosis.

While the focus of orthotics studies have been on the rearfoot, orthotic devices are also prescribed to runners with overuse injuries of the knee. Pronation of the subtalar joint is coupled with internal rotation of the tibia, which, in turn accompanies flexion of the knee (Hamill et al., 1992; McClay and Manal, 1997). Therefore, restricting movement of the rearfoot complex may indirectly control knee motion and result in alleviating knee pain (Eng and Pierrynowski, 1993; Way, 1999). However, few studies have examined the effect of foot orthotics on knee mechanics. Furthermore, no studies have assessed the effect of a foot orthosis on the knee kinematics of a FFS pattern.

The purpose of this study was to compare the effect of orthotic intervention on the rearfoot motion of both a FFS and RFS pattern. It was hypothesized that FODs would decrease peak rearfoot eversion, eversion excursion, and eversion velocity with a RFS pattern but not with a FFS pattern. It was also expected that orthotics would decrease knee abduction and internal rotation in the RFS pattern but not in the FFS pattern as these motions are associated with pronation.